Elelctromagnet.



C. F. BALDWIN. ELECTROMAGNET.

APPUCAHON HLEU SEPT. 3, 1915 Patented July 2. 1918.

In ven for: Char/es F Ba/dw/n Wi/n ess es:

UNITED STATES PATENT OFFICE.

CHKRLES FOWLER BALDWIN, F MONTCLAIR, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGNMENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORA- IION OF NEW YORK.

ELECTROMAGNET.

Patented July 2, 1918.

Application filed September 8, 1915. Serial No. 48,2:

T dime/ram it may concern:

B e it known that I, CHARLES FOWLER BALDWIN, a'citizen of the United States, residing at ontclair, in the county of Esseiiiand State of New Jersey, have invented certain" new and useful Improvements in Electromagnets, of which the following is 7 a jfiiligiclear, concise, and exact description.

' ,Tliis' invention relates to electromagnets,

10 and more particularly to electromagnets provided with means for retarding the reaction of the same. I The object of this invention is to providean inexpensive and efiicient slow acting el'ectromagnet.

According to this invention a lurality of actuating windings are provi ed' on the magnet core, one of said wlndings serving toretardthe reaction of the magnet upon he denergization of another winding.

The magnet may be adjusted in such a maniierfthat by providing a high resistance actuating Winding and a 16w resistance locking winding,the lockingwinding would vii it Q 80 of force when the current through the ener- 'serve to retard the reaction of the magnet ,npc n the deenergization of the high resistance' winding. his arrangement is based on the well-known physical laws gov eaning the reduction of the magnetic lines gizingi winding is broken. If a magnet, on the core of which a single winding is proyided, will releasc on onethird of its oper ating ampere turns in a certain interval, it

:willrequ1re more time to release if one-sixth of its operating ampere turns is supplied by a second winding, the cr rrent through W ich is not broken until t e magnet re- 7 leases 0 This invention is described; and shown in *the drawings as embodied inga selector circuit for automatic telephone exchanges. 'It

'will be obvious, however, that magnets constructed in accordance'with the present in- 4 vention are adapted for use in circuit arrangements of widel varying character.

I The invention wil be more fully understood from the following detail description and the appended claims.

o -T-he Jcalhng subscriber located at substa- -tion 1, desiring to establish a connection witha called station 2, removes his receiver from the switchhook, causing thereby, in P the nvell-known manner, the selection of an coming line circuit, side-switch wiper 7 and the right-hand winding of relay 5, to ground. Relay 5 becomes energized and closes an energizing circuit from ground through its front cbntact, contact 8 gcloscd as long as selector 3 is in its norma position), and the high resistance right-hand winding of a magnet. 9, to grounded battery. Magnet 9 becomes energized and closes a locking circuit for itself from ground through its low resistance left-hand Winding, left-hand front contact and armature, and the winding of a release magnet 10, to grounded battery. The current flowing through this locking circuit is not of suf ficient strength, however, to energize release magnet 10. The calling subscriber proceeds now to cause the setting oflselector 3, in accordance with the numerical designation of the called substation, by operating a calling device 11 provided at substation 1. Upon each interruption produced in the line circuit, relay 5 closes a circuit from ground through its armature and back contact, side-switch Wiper 12, the right hand armature and front contact of magnet 9, a side-switch wiper 13, and the Winding of primary magnet 14 to grounded battery. Under the control of magnet 14 the brushes of selector 3 are moved in a rotary direction.

Upon the first release of the armature of .relay 5, the original energizing circuit of magnet 9 was opened. Magnet 9, however, does not become denergized in response to this short interruption produced in its energizing circuit, it being maintained actuated by the above traced locking circuit.

The left-hand winding of magnet 9 is composed of fewer turns 'than the righthand winding, and is not strong enough to maintain the magnet locked up.

The magnetic flux due to the closure of the actuating circuit, includin the right-hand winding, produces a potentlal in the locking winding, said potential havin the tendency to oppose the battery potentia of the-circuit including the left-hand winding. Upon a;

interruption in' the circuit, including the right-hand winding, the magnetic flux gradually collapses, but its reduction is retarded due to the effect of the additional field pro-' that upon an interruption of the actuatin circuit the collapsin magnetic field is aide by the potential produced in the circuit of 20 the other winding.

Magnet 14 stops the selector brushes, and, upon the completion of the first stop, this magnet closes its back contact as soon as the armature of line relay disongages its 26 back contact. Therefore, upon the second deiinergization of relay 5 a circuit is established from ground through the armature and back contact of line relay 5, side-switch wiper 12, the right-hand armature and front 80 contact of magnet 9, the armature and back contact of magnet 14, contact (closed as soon as selector 3 leaves its normal position), and the high resistance right-hand winding of magnet 9, to grounded battery. Thus, during the vibration of the armatures of line relay 5 and primary magnet 14, the magnet 9 remains energized, the continuously closed locking circuit retarding the reaction of the magnet while the actuating circuit of the same is momentarily interrupted.

After the subscriber has sent out the desiredseries of impulses, the armature of line relay 5 is maintained attracted, and no circuit will he found for: the high resistance winding of magnet 9, whereupon this magnet will slowly release." Upon the deiinergization of magnet 9, the 'sideswitch wipers are moved into position 2, in WhlCll POSlllLOIl magnet 14 is disconnected, and a circuit is established from ground through an overflow contact 16 (open only if all the trunks in the selected group are busy), armature and back contact of a secondary magnet 17,

side-switch wiper 18 and the winding of relay 19, to grounded battery. Relay-19 closes a circuit from ground through its armature and front contact, side-switch wiper 20, the right-hand back contact and armature of magnet 9, side-switch wiper 12,

battery. Magnet 17 becomes energized and opens the circuit of relay 19, which in turn causes the denergization of magnet 17'and the reestablishment of its own circuiti. It 66 will be seen thus that magnet 17 is interand the winding of magnet 17 to grounded ruptedly energized and deenergized for causing the stepping of the selector brushes in a vertical direction.

As well known, the busy or idle condition of outgoin lines or trunks is determined 70 by a potentlal placed upon multiple test terminals, such as 21. Supposing that in this case the busy condition of outgoing lines is characterized by a battery potential placed upon. the test terminal 21, and the idle con dition of such lines by a ground connection at terminal 21, it will be seen that as soon as an idle outgoing line is reached, a circuit is established from such ground through test terminal 21 and a test wiper 22 of selector 3, side-switch Wiper 23, and the right-hand winding of escapement magnet 9 to rounded battery. Escapement magnet 9 ecomes energized and moves now, upon its energization, the sideswltch wipers into position 3 55 for disconnecting the secondary magnet 17 and connecting the calling incomin line at side-switch wipers 6 and 7 throug to the selected outgoing line. The subscriber at substation 1 will cause now the complete establishment of the desired connection. In position 3 of the side-switch wipers, relay 5 and magnet 9 are deenergized.

Upon the severing of the established connection at the called station 2, a ground 96 (which was disconnected after the seizure of an idle outgoing line by selector 3) is connected through test terminal 21, test brush 22, side-switch wiper 23, the left-hand back contact and armature of magnet 9, and the winding of release magnet 10 to grounded battery. Release magnet 10 becomes ener- 'zed and closes a locking circuit for itself rom groun through its right-hand armature and front contact, a contact 24 (closed as soon as selegtor 3 leaves its normal position), and the winding of this magnet to grounded battery. Under the control of ma et 10, selector 3 and the associated side-switch are restored to normal, the lockin circuit for 110 said magnet being maintained ciosed as long as contact 24 is closed, i. 6., until selector 3 reaches its normal position.

There is shown at the left-hand armature of magnet 10 a wellknown anti-sparking 115 device comprising a condenser, a resistance and a grounded battery, which serves to prevent the sparking at the operating contacts of the magnets associated with the selector.

What is claimed is:

1. In a telephone exchange system, incoming lines, outgoing lines, a selector switch for interconnecting an incoming line with an outgoing line, a test brush, an impulse receiving means, a source of current, a plural- 126 ity of operating magnets for said switch, a magnet for controlling the operation of said magnets, a winding on said controlling ma net arranged when energized to attract tE armatures of said controlling magnet, an- 180 other winding on said controlling magnet arranged when energized to retard the retraction of the armatures of said controlling magnet but unable to attract or maintain said armatures attracted, means controlled by said impulse receiving means for completing a circuit for said first mentioned winding, means including the test brush for completing another circuit for said first mentioned windin and means for completing a circuit for said second .mentioncd winding in series with said source of current.

2. .In a telephone exchange system, incoming lines, outgoing lines, a selector switch for interconnecting an incoming line with an outgoing line, a test brush, an impulse receiving means, a source of current, a plurality of operating magnets for said switch, a magnet for controlling the operation of said magnets, a high resistance winding on said controlling magnet arranged when energized to attract the armaturcs of said cont'rollin; magnet, 'a low resistance winding on said controlling magnet a ranged when energized to retard the'ret'raction of(thc armatures 0' said controlling magnet lnltunable to attract or maintain said armatures attracted. means controlled by said impulse receiving means for completing a circuit for said high resist ance Winding, means including, said test brush forcompletin' another circuit for said high resistance Winding, and means for complating a circuit for said low resistance Winding in series with said source of current.

In witness whereof. I hereunto subscribe my name this 28th day of August A. l). 1915. 

